Anisotropic failure criterion for evaluation of local necking after nonlinear deformation history in sheet metal forming processes

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The prediction of formability is one of the most important tasks in sheet metal process simulation. The common criterion in industrial applications is the Forming Limit Curve (FLC). The big advantage of FLCs is the easy interpretation of simulation or measurement data in combination with an ISO standard for the experimental determination. However, the conventional FLCs are limited to almost linear and unbroken strain paths, i.e. deformation histories with non-linear strain increments often lead to big differences in comparison to the prediction of the FLC. Volk published a phenomenological approach, the so-called Generalized Forming Limit Concept (GFLC), to predict the localized necking on arbitrary deformation history with unlimited number of non-linear strain increments. Anisotropic material behavior is not considered in the GFLC so far.The main focus of the proposed research project is the experimental characterization of the forming limits depending on the rolling direction (anisotropy) and the forming history. The experiments will be performed mainly on the universal testing machine BUP1000, funded by DFG (INST 95/1268-1). Based on the experimental database a parameterization of the strain paths and an expansion of the metamodel with the anisotropic material behavior takes place. Finally, the identification of the material influence on the developed procedure and derive of a scaling approach for material families complete the research project.The expected results enable the evaluation of non-linear strain path by the consideration of anisotropic material behavior.